2 Koi Ponds. High Nitrates

One fish in the large pond has bulging red eyes, another has a big bulge on the side of its body.

770gallon pond, 3.5ft

20 large koi, pond 6 years old:

KH 30

GH 20-40

Ammonia 0.1

Nitrite 0.1-0.3

Nitrate 50

He appears to have a problem with high nitrates and low KH and low GH. He had to keep doing water changes to keep nitrates low or they can exceed 100ppm. The ponds are quite full with koi and they swim slowly.

Each pond has a small waterfall that brings water down from above and a filtration fixture at the bottom on the pond that sucks debris out to an external canister. The larger pond has a fixture at the bottom of the deep end that can push water upwards with surface action like a pond pump.

There are constant low levels of salt (0.12) in the ponds to prevent infection.

I’ve forwarded this site to Dad’s friend and linked this blog post to him. Hoping he can followup with you here on how to treat.

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6 Comments

Excellent. So glad to hear you’re already buffering. Michele is now a pro at it. You’re in good hands

I’m not fond of UV lights; they keep a natural ecosystem from forming, destroying all living organisms. Pond keepers rely on UV lights and meds for healthy fish, when all they needed to do was improve the water quality. Algae is made up of micro organisms; diatoms. It’s the living plant, and while the light has kept your water free of green water algae, it’s also kept it from having substrate; the good kind

This could be the cause of the small readings for ammonia and nitrite. Given the chance, UV lights will also destroy beneficial bacteria. They don’t float freely in the water, but the sterile environment could discourage their formation. There are many living organisms in our ponds that work together in building a healthy ecosystem. If the water is healthy, the ecosystem will be healthy, as well as the life in it

Our fish create waste, and from waste, ammonia is created. When it’s present, beneficial bacteria form to feed on it, converting it into nitrites. When nitrites are present, another type of friendly bug forms to feed on it, turning the second toxin to form in the cycle, into nitrates. They say nitrates are the end result of the nitrogen cycle, but this is untrue. When nitrates are present, algae forms, providing a food source for the fish, while eliminating nitrates. It’s the true end result of the cycle, but also the beginning, completing the aqua cycle of life

It’s also possible the fish are eating the algae. LOL I get carried away sometimes don’t I?

I’m totally into organic fish keeping. My tank hasn’t seen a chemical in five years now, and hopefully, never will again. I don’t even use water treatment to convert chlorine. Being a liquid gas, it’s easily eliminated by exposing it to fresh air or oxygenated water. I’m not sure if you have chlorine or chloramines, which are chlorine and ammonia combined. If this is the case, you should be adding water treatment that converts the disinfectant before adding or exchanging water

Fish keepers are really attached to their bubblers, but useless for oxygenating water, although, if yours is powerful enough, it may disturb the surface, which is beneficial, but in a very small way

Thanks Venus, Already got some instructions from Emme & dosed quite amount of baking soda + Epsom salt yesterday. Will test later today to see what the total dosage I might need. Perhaps the UV doing their job, I don’t have much green water problem. Algae are found on the liner but not heavy. Will check out pond pump in the market and turn on the air diffuser of the bottom drain more frequently.

Small Koi; it’s about time. Maybe they’ve been around for some time, and I just never heard of them, but good to know. I keep goldfish

You can handle the overstocking issue, but only if the water is excellent. Healthy fish live in healthy water

Let’s start with my favorite lesson; oxygenating water. Water becomes oxygenated by means of diffusion; meaning the surface movement pulls oxygen molecules from the air above. In order for this to happen, the body of water must be free and clear. There are a few things that cloud water, and the first on the list is carbon dioxide, a gas created from the waste your fish produce. It’s harmless enough, but it takes up space, keeping oxygen from entering. The filtering systems you have don’t provide the necessary action needed to eliminate gases.

Surface movement pushes Co2 out as it pulls oxygen in, but the surface of our ponds is small compared to the body of water, so we have to make a few compromises, and that compromise is called a pond pump. Only a real pond pump has the potential. This is because it sits on the floor, taking water from the very bottom (where gases hang out) and then shoots it to the surface in a powerful jet stream where the gases are eliminated

Because of your stocking level, and the amount of gases being produce, I would get a 1000 GPH for the small pond and two 2500 GPH for the larger pond. Sizing a pond pump depends on the amount of surface area and the depth of the pond as well as the stocking level

Do you have algae? I couldn’t tell from the photos. A lot of pond keepers think of it as grunge, but it’s very beneficial. It consumes nitrates like no other plant, and is a valuable food source for the fish. In slow moving ponds, mostly green water or blanket algae forms. These are the types that reduce oxygen levels; one by filling the body of water, the other by covering the surface. The only good algae is substrate algae. It forms on the surface of just about anything as long as it’s in water, and only when nitrates are present. Green water and blanket algae form only when the water is slow moving, and yet another reason to include pond pumps in your set up

All too many pond keepers use treatments to eliminate algae; dangerous for the fish and the friendly bugs that create the nitrogen cycle

Next to pH, algae is the most misunderstood topic in the industry

Yes, pH is next on our list of how water is oxygenated. pH was originally a theory, not a parameter, but the industry changed this, leading us to believe that pH is responsible for alkalinity, but it’s not. Carbonate mineral (KH) alone has this responsibility. pH testers pick up alkalinity readings, but it also measures oxygen. If we understand this, we can use pH testers for testing oxygen.

Carbonate mineral gives water the ability to support oxygen. Your alkalinity levels are extremely low; meaning the water is acidic. This is what’s causing the sickness in your ponds. Bad bacteria thrive in water low in oxygen, so the key is to create an environment that they can’t tolerate. It just so happens that our fish and the beneficial bacteria that share their living quarters, thrive in heavily oxygenated water

They say the comfort zone for KH is 70 to 120 ppm, but why settle for less? A reading of 70 is in the neutral zone; the line between alkalinity and acidity; too close for comfort

GH (general hardness) is made up of two parts magnesium and one part calcium. These are minerals your fish need for good health. The comfort zone is 200 to 400 ppm

Carbonate mineral, magnesium and calcium; these are the three major minerals are fish need for good healthy. Most regions are low in magnesium, and rich in calcium, so we normally buffer GH with Epsom salts, which is pure magnesium. It’s my guess that the low reading you”re showing for GH is calcium

To summerize, add a few pond pumps to your set up and buffer the mineral value, and your fish will come to life

Toby, I wrote you the longest post this morning, but lost it; something I haven’t done in a very long time. Give me a little time, and I’ll rewrite it, but I do want to say, I’m delighted to see you here

Thanks Venus for good advise. Reducing the number of koi is in my mind, but before I have to let go can I salvage whatever I could to improve their health. Part from 33 koi most are below 12″ and non Japanese breed, they won’t grow big. So hoping I can still run them for another year or so before things gone worse. The bulging eye fishes seems under control after frequently water changes. Apart from water changes, does running the water through roots of water plant helps lowering the nitrate a lot? The above ground pond doesn’t have much temps problem as I can maintained them throughout hot & cold weather. The walls are insulated! Does spawning activity cause foam in water?

Ponds above grade don’t have the luxury of the insulation that the earth provides, and in your part of the world, this is all important. The pond is probably too warm in the summer and too cold in the winter. This is something to bring to Toby’s attention; to test temps. If temps get to 80f at the bottom of the pond, time to ice the water. Obviously the ponds aren’t freezing solid, or the fish wouldn’t make it through the winter, so that’s good

It looks like the larger pond is partially below grade; is that right?

If Toby has the budget, there are both pond heaters and coolers, but a bag of ice in the summer works just as well. It’s a little more difficult to warm pond water in the winter, but heaters are affordable

Two ponds, and both overcrowded. Nitrates will always be an issue. Unfortunately, most folks have no idea how large Koi grow, and from the looks of it, they have a lot of growing to do, and no room to do it

I don’t see any signs of algae, but looks are deceiving. It’s my guess he’s using algae remover. Advise him to stop if this is the case. Algae will control nitrates, although, being in tight quarters, it’s possible the fish are eating the algae as it grows. Overstocking leads to a multitude of issues

You didn’t list pH, but you don’t need to. I can tell by the low KH and the quiet surfaces in the photos that oxygen levels are too low. The fish are lethargic because of it. If nitrates were bothering them they would be hugging the bottom. The increased water pressure relieves the pressure caused by nitrates

Nice construction; nice looking ponds

It’s next to impossible to rehome sickly Koi. I know you guys took 10 fish, and that was really kind of you, but I doubt anyone is going to line up. The average pond keeper has poor water quality anyway, sad to say

The problem with Koi, if the fish are healthy, they spawn, adding to the stocking level. Feeding less could encourage the fish to eat the eggs they produce. I doubt there’s a lot of spawning going on in Toby’s pond, but for future reference, you’ll see fish chasing each other, and often leaping out of the water. The males chase the females until they become too exhausted to swim. Then they rub and bump against her. The pressure helps to release the eggs. The males fertilize the eggs as they’re being released. In most ponds, the eggs are quickly eaten, and if any hatch, the small fry may be eaten as well. Koi have no maternal instinct

When you see spawning activity, and you will see it if you’re around, skip a meal

I recommend the very same for Toby as your parent’s pond. Buffer GH and KH. Add a pond pump to the small pond and two to the big one, and things will start turning around. If we could improve the health of these fish, maybe you could talk Toby into selling a few. Koi are worth a pretty penny; especially large ones. If he just can’t let go, maybe you can talk him into a larger pond. Even if he can improve the health of the fish, they’ll still be miserable. Fish need space to swim; to be fish, and Koi, growing up to 3′ in length, need a heck of a lot of it